They're trying to validate that you're using a trusted version of AGESA.
This is probably intentional, the AMD bulletin[^1] mentions this (ie. for Milan):
> Minimum MilanPI_1.0.0.F is required to allow for hot-loading future microcode versions higher than those listed in the PI.
Now that runtime loading of microcode patches cannot be implicitly trusted, the machine should not attempt to prove AMD's authorship of the newly-loaded patch without a concrete guarantee that the current microcode patch is trustworthy.
Presumably (load-bearing italics), the contents of an AGESA release (which contains the patch applied by your BIOS at boot-time) can be verified in a different way that isn't broken.
under agesa 1.2.0.2b
> microcode: CPU1: update failed for patch_level=0x0a60120c
under agesa 1.2.0.3a PatchA (which asus leaked that it fixes this issue)
> microcode: Updated early from: 0x0a60120c